You're the one thinking, how the **** am I supposed to know how long it will take you? Took you about 5 minutes to decide pedophile/child was OK.
I'm just making assumptions based on human nature. So I'll ask you this. You have a female lover, long-term relationship. You'd like marriage but she has a female lover, also a long-term relationship, and you're cool with it because you're able to stick something in there every now and then if you know what I mean. You three live together. Suddenly polygamy is accepted/allowed. Your long-term lover says "I want to marry Martha but not you." You good with that?